YOUNG AT HEART: Marcus Camby, smiling at practice last month, is one of five Knicks players over the age of 35 entering this season.Bill Kostroun

We understand 40 is the new 30 thanks to Dr. Oz and all the health and fitness instructors who educate us on better exercise methods and eating habits.

We’ve seen it play out in the world of sports recently. Bernard Hopkins became the oldest man to win a boxing title when at age 46 he captured the light heavyweight champion by beating Jean Pascal on May 21, 2011.

Randy Couture won his last MMA title at age 43 and Tom Watson came one putt short of winning the British Open at age 59.

We’ve also seen it work in team sports as well. The late George Allen put together the “Over-The-Hill-Gang” when the starters on his 1971 Redskins team averaged 31 years old. They would reach the Super Bowl after the 1972 season, losing to the undefeated Dolphins.

When the 2012 NFL season began, the Ravens had the oldest starting offense in the league averaging 28.7 years of age, while the Steelers had the oldest defense at 30.1, according to ESPN.

Now the 2012 Knicks are trying to extend Father Time with a 15-man roster that averages 31.25 years, making them the oldest NBA team this season with five players over the age of 35.

Large quantities of Advil figure to dominate the Knicks locker room throughout an 82-game season that begins tonight against the Heat as defying age figures to be just as big a challenge as beating their East Conference opponents.

In speaking to an attorney who advises professional athletes, his theory about age was this: “They don’t really lose their skills in a straight line, they just have more bad days.”

For the Knicks, those bad days could equate to poor shooting performances, nights when their instincts are a bit slow or their bodies feel heavy or their legs are tight. The back-to-back games figure to be brutal.

If this were 2002, the Knicks would almost certainly be an elite team, but their age casts an uncertainty over whether they can hold up long enough to challenge for a high seed in the playoffs.

You get the feeling the Knicks are a lot like the Yankees, hoping older veterans will hold on long enough to where their experience will give them an edge. Only it didn’t work for the Yankees, and chances are it won’t work for the Knicks.

The NBA is a young man’s game, played above the rim. The half-court, slow down, isolation game is gone, even though it’s the best way for Carmelo Anthony to get 30 points. Today’s NBA is about keeping pace with LeBron James, Dwyane Wade, Kevin Durant and Blake Griffin. Heck, Kobe Bryant is starting to look an old 34, entering the season with a foot injury that figures to limit his ability.

On paper, there is reason to be optimistic about the Knicks’ chances. The best case scenario is Jason Kidd (age 39), Kurt Thomas (40), and Marcus Camby (38) will bring strength and leadership to the Knicks. Anything from Rasheed Wallace (38) would be gratis.

But it’s all window dressing unless they can stay on the court long enough to develop the kind of winning chemistry that can lead to a championship. Amar’e Stoudemire is already out with a knee injury and Camby is nursing a strained calf. Wallace isn’t even in basketball shape.

The grind of the 82-game season will test the strength and depth of a team. Right now we can’t be sure if the Knicks have enough of either. If the geezers can hold up until Iman Shumpert returns from his knee injury and Stoudemire is healthy again, then the Knicks may have something. But from this view, it appears this “Over-The-Hill Gang” will be fighting uphill most of this season.